Magnetic Interactions Between Radical Pairs in Chiral Graphene Nanoribbons

Wang, Tao; Sanz, Sofía; Castro‐Esteban, Jesús; Lawrence, James; Berdonces‐Layunta, Alejandro; Mohammed, Mohammed S. G.; Vilas‐Varela, Manuel; Corso, Martina; Peña, Diego; Frederiksen, Thomas; Oteyza, Dimas G. de

doi:10.1021/acs.nanolett.1c03578

Cited by 44 publications

(46 citation statements)

References 51 publications

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“…A magnified STM image (see Figure c) manifests that this self-assembly contains rod-like species of two orientations. Typically, the oxygen-containing group terminal appears darker than the phenyl terminal, considering that the oxygen end is closer to the surface. , By tentatively superimposing scaled molecular models onto Figure c, we attained a structural model with diverse binding motifs. The potential −OH···OH– and −OH···H-ph HBs are marked with dashed white lines.…”

Section: Results and Discussionmentioning

confidence: 99%

Sequential Activation of Aromatic C─H Bonds on Cu(111)

et al. 2022

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avenue to prepare carbon-based nanomaterials. The emerging on-surface synthesis offers an unprecedented opportunity to achieve aromatic C−H activation on metal surfaces. Previous works mostly focus on the activation of either C−H bonds of phenyl rings or C−H bonds of functionalized aromatic rings. The research on the activation priority of two aromatic C−H bonds within a molecule has remained unreported. In this work, starting from a building block comprising both phenyl and phenol rings, we achieve the sequential activation of ortho C−H bonds of the phenol ring and meta C−H bonds of the phenyl ring on Cu(111) via stepwise annealing. During annealing, the hydrogen bond-and coordination interactionstabilized chiral nanostructures are observed successively below 450 K. At 450 K, covalent dimers and trimers originating from the activation of ortho C−H bonds of phenol ring are generated. Annealing to 500 K gives birth to the complex covalent polymers formed by the further activation of meta C−H bonds of phenyl ring. The morphologies of these nanostructures are resolved by scanning tunneling microscopy (STM). The synchrotron radiation photoemission spectroscopy (SRPES) is utilized to follow the chemical states of surface species during the reaction process. This work determines the activation priority of two aromatic C−H bonds. The attained principle could be potentially used to guide the hierarchical C−C coupling on metal surfaces.

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Section: Results and Discussionmentioning

confidence: 99%

Sequential Activation of Aromatic C─H Bonds on Cu(111)

et al. 2022

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“…Specifically, the 120 • phase is expected to be the broken symmetry ground state in a triangular lattice with AF interactions. We note that the PBE functional has been previously used to model exchange interactions in planar nanographenes, with the comparison with experiments in fair agreement [52].…”

Section: Magnetization In the Crystal Phasesmentioning

confidence: 52%

Frustrated magnetic interactions in a cyclacene crystal

Ortiz

Sancho‐García

Fernández-Rossier

2022

Phys. Rev. Materials

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We study the emergence of magnetism and its interplay with structural properties in a two-dimensional molecular crystal of cyclacenes, using density functional theory (DFT). Isolated cyclacenes with an even number of fused benzenes host two unpaired electrons in two topological protected zero modes, at the top and bottom carbon rings that form the molecule. We show that, in the gas phase, electron repulsion promotes an open-shell singlet with strong intramolecular antiferromagnetic exchange. We consider a closed packing triangular lattice crystal phase and we find a strong dependence of the band structure and magnetic interactions on the rotation angle of the cyclacenes with respect to the crystal lattice vectors. The orientational ground state maximizes the intermolecular hybridization, yet local moments survive. Intermolecular exchange is computed to be antiferromagnetic, and DFT predicts a broken symmetry 120 • spin phase reflecting the frustration of the intermolecular spin coupling. Thus, the cyclacene crystal realizes a bilayer of two antiferromagnetically coupled S = 1/2 triangular lattices. Our results provide a bottom-up route towards carbon based strongly correlated platforms in two dimensions.

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“…22−24 GNR heterostructures have also been produced by covalently bonding GNR segments having different electronic characters, showing promise for use in electronic devices such as fieldeffect transistors (FETs). 25−31 Topological engineering, 24,32−35 metallicity, 36 and magnetism 37,38 have all been successfully implemented in GNRs, further consolidating them as attractive nanomaterials for use in spintronic, qubit, and memory devices. 39−46 Despite this progress, however, it is still not possible to synthesize monodisperse GNRs having well-defined length or well-defined heterogeneous monomer sequence, important milestones that would enable new GNR functionality through flexible electronic interface engineering.…”

Section: ■ Introductionmentioning

confidence: 99%

Programmable Fabrication of Monodisperse Graphene Nanoribbons via Deterministic Iterative Synthesis

et al. 2022

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While enormous progress has been achieved in synthesizing atomically precise graphene nanoribbons (GNRs), the preparation of GNRs with a fully predetermined length and monomer sequence remains an unmet challenge. Here, we report a fabrication method that provides access to structurally diverse and monodisperse “designer” GNRs through utilization of an iterative synthesis strategy, in which a single monomer is incorporated into an oligomer chain during each chemical cycle. Surface-assisted cyclodehydrogenation is subsequently employed to generate the final nanoribbons, and bond-resolved scanning tunneling microscopy is utilized to characterize them.

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Magnetic Interactions Between Radical Pairs in Chiral Graphene Nanoribbons

Cited by 44 publications

References 51 publications

Sequential Activation of Aromatic C─H Bonds on Cu(111)

Sequential Activation of Aromatic C─H Bonds on Cu(111)

Frustrated magnetic interactions in a cyclacene crystal

Programmable Fabrication of Monodisperse Graphene Nanoribbons via Deterministic Iterative Synthesis

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